fc with 105W CFL

[calvin_orchidL]

Originally Posted by Ross

If this is true, why are all the t5 commercial units lined with German reflective aluminum? I agree brushed foil might scatter light, but the shiny side should reflect light. Would be easy to either prove or disprove, though.

The issue is that with aluminum foil, it crinkles such that unless you had it perfectly fresh and flat, the amount of returns you get in terms of reflective capacity is gone from the light scattering...hence the utility of mylar/german reflective aluminum but uselessness of foil. With a DIY setup, a white surface is much easier to produce than a flawless aluminum foil setup, imo. I suppose if you cut it incredibly carefully and glued it on without botching it, it would work...I'm just reporting what I've heard from some very experienced hemp growers

[LinhT]

Great points, Ross and Calvin. All these issues did cross my mind. Actually, I have searched through many light units online and most of the expensive ones seem to always have the German aluminum reflector and I did read somewhere that aluminum supposedly gives the best reflection of light. I was using aluminum reflectors for a while with some smaller CFL's. Since I don't have a case to grow in, I have to rely on my giant humidifier to increase humidity in that room. With the aluminum reflectors, my humidifier could be running full force all day but the humidity in the area underneath the bulb + reflector was always under 60%. When I put my hand above the plants it felt like there was significantly more heat in that area with the aluminum reflector vs. this plastic Ikea bucket thing. With this white reflector I can easily maintain 75& or greater humidity with the humidifier. Initially, I was looking for an even smaller "Ikea bucket thing" because I too, thought the bulb needed to be closer to the reflector to be of use. However, that 105w CFL does give off quite a bit of heat the closer you get to it so I wasn't sure if it was safe to have it so close to the reflector since it is not aluminum. I am surprised at the FC's Jim measured at 6 and 8 inches. I didn't think it would be that high. Also, from what I understand, 2500 fc under lights is not the same as 2500 fc in a greenhouse. However, I think Jim has 5 times the number of orchids I have and they all look fabulous so I'm giving this a try. The only way I will know how effectively the setup works is wait till next summer and see if my 10 neos bloom again. I sure do appreciate all the expertise you "light" people share though.

[LinhT]

Originally Posted by calvin_orchidL

The issue is that with aluminum foil, it crinkles such that unless you had it perfectly fresh and flat, the amount of returns you get in terms of reflective capacity is gone from the light scattering...hence the utility of mylar/german reflective aluminum but uselessness of foil. With a DIY setup, a white surface is much easier to produce than a flawless aluminum foil setup, imo. I suppose if you cut it incredibly carefully and glued it on without botching it, it would work...I'm just reporting what I've heard from some very experienced hemp growers

Calvin,
I have read through some websites on how to build reflectors for growing weed and they are, um, pretty creative.

[Ross]

Originally Posted by LinhT

Great points, Ross and Calvin. All these issues did cross my mind. Actually, I have searched through many light units online and most of the expensive ones seem to always have the German aluminum reflector and I did read somewhere that aluminum supposedly gives the best reflection of light. I was using aluminum reflectors for a while with some smaller CFL's. Since I don't have a case to grow in, I have to rely on my giant humidifier to increase humidity in that room. With the aluminum reflectors, my humidifier could be running full force all day but the humidity in the area underneath the bulb + reflector was always under 60%. When I put my hand above the plants it felt like there was significantly more heat in that area with the aluminum reflector vs. this plastic Ikea bucket thing. With this white reflector I can easily maintain 75& or greater humidity with the humidifier. Initially, I was looking for an even smaller "Ikea bucket thing" because I too, thought the bulb needed to be closer to the reflector to be of use. However, that 105w CFL does give off quite a bit of heat the closer you get to it so I wasn't sure if it was safe to have it so close to the reflector since it is not aluminum. I am surprised at the FC's Jim measured at 6 and 8 inches. I didn't think it would be that high. Also, from what I understand, 2500 fc under lights is not the same as 2500 fc in a greenhouse. However, I think Jim has 5 times the number of orchids I have and they all look fabulous so I'm giving this a try. The only way I will know how effectively the setup works is wait till next summer and see if my 10 neos bloom again. I sure do appreciate all the expertise you "light" people share though.

Linh, a couple issues. First, the t5 lights are designed to operate at 95 degrees F. This is not hot enough to burn anything, but plastic might sag a bit. It also explains the heat rise. Second, The warmer the air, the lower the "relative humidity" will be. Third, Jim got double the foot-candles you will get if he is using two bulbs and you are using one bulb. His measurements are just about double what I was reading with one bare bulb. Aluminum foil cemented carefully and smoothly (shiny side toward the bulb) to the inside of the reflector/bin will easily increase reflectance. I don't see how it would not. I use plain aluminum foil on inside of my grow window walls and the increase is measurable over white painted walls.

[LinhT]

Ross,

You said by putting in that layer of aluminum I can nearly double the fc's, right? So if I add the aluminum then I can potentially get somewhere close to Jim's 2 bulb readings with my one bulb?? Do you think I need to move the bulb up closer to the top of the reflector too?

I think I may have to break down and get one of those $100 light meters you've recommended so many times. I have 2 of these light units so I might do the aluminum thing on one and leave the other alone. Then take measurements with the meter to see what I get....

[Ross]

I don't want to decieve you. I ment you would increase the levels substantially, but double? Maybe not. I'd say you might expect 200-400 additional footcandles from the same bulb. By all means spring for a decent light meter. It's not just the setup you want to check, but the output over the year. You want to know when you need to replace the bulb.

[calvin_orchidL]

Here's an experiment Brooke did that was posted on another forum a while back - she extended her lamps with aluminum foil reflectors and measured light readings at various distances:

Here's the link

Note that this was a lamp style setup, with the DIY reflector quite close to the bulb. I'm not sure whether having a reflector 4" away from the bulb will reflect a whole lot of light downwards, but hey, it's worth a shot

[jim blanford]

Hey..Calvin your right that light is about 2ft above the plants and they are Cycnoches, Bulbos, Phals, Phrag seedlings, a Neo, a Sedirea, I also use it as a staging area for plants in spike the lower light makes the spike get taller or helps straighten it, also plants just repotted adjust better there.